Clones bear a striking physical resemblance to their genetic donors, much like identical twins, though usually with a time delay. Behavioral similarities, though harder to quantify, are often evident as well.

To see the resemblance between Missy and her clones, please visit the Cloning Missy section and check out A Rose is a Rose. Below is a more general discussion on resemblance among clones.

Physical Resemblance
There is no question that clones bear a close physical resemblance to their genetic donors, as demonstrated by the hundreds of clones produced to date in various species. The picture to the left of two cloned cows shows a striking physical resemblance, which is typical of clones of whatever species.

One notable exception is CC, the world's first cat clone. CC had coat colorings that differed from those of Rainbow, her genetic donor, a calico. However, due to an effect known as X-linked inactivation, the clones of calico cats will always look different from their donors. However, in any other breed of cat, and all breeds of dog, a clone should look like the identical twin of its genetic donor.

Behavioral Resemblance
The question of behavioral resemblance – commonly termed "personality" – between clones and their donors is much more hotly contested than physical resemblance. The most widely held theory on animal behavior is that it's shaped by a mix of genetic and environmental factors. Two behavioral traits with strong genetic bases are intelligence and temperament, as demonstrated by differences in these traits between dog breeds such as Border Collie, Golden Retriever, and Pit Bull. Although environmental factors can shape the behavior of individuals to a certain degree, anyone who has worked with these breeds knows that their behavioral responses, such as herding in Collies and retrieving in Retrievers, are hardwired to a large degree. It is not unreasonable to assume that specific behaviors in individual dogs (and cats) may also have genetic bases, and thus may be present in clones of these individuals. Behavioral resemblance can potentially be amplified by duplicating as closely as possible the conditions under which the donor was raised.

So far, Missy’s family reports that her clones exhibit many of her behavioral tendencies – intelligence, language comprehension, passion for her people and extremely physical play. Missy and her clones also share an unusual love of steamed broccoli – hardly a common dog favorite.

Ultimately the question of behavioral resemblance between pet clones and their donors will not be conclusively resolved until we've produced more clones of beloved pets, whose owners can then provide both anecdotal comparisons and formal responses to questionnaires prepared by behavioral geneticists. This combination of approaches should generate more meaningful data than formal lab-based behavioral studies by themselves.

A final thought: Many pet owners feel that they made certain mistakes raising their exceptional pets. Now that they know what their pets are capable of and what training approaches are and are not effective, some feel they can do a better job raising the clones than they did with the genetic donors.